When the engine is in the warm state, air-fuel ratio in the economy match in 13˜15:1 set by the factory, but the engine in the cold start need 6˜12:1 air-fuel ratio, so when the engine starts, the carburetor needs to provide additional fuel to the engine to ensure that the engine can start normally.
At present, the choke device is widely used to reduce the amount of air intake to get more fuel for the start, specific steps: the first step, squeeze the purge bulb; the second step, close the choke; the third step, open the throttle fully or set the throttle in the fast idle speed position; the fourth step, pull the engine starter, hear POP sound so far; the fifth step, pull the choke to the ½ position; the sixth step, pull the engine starter to the engine running; the seventh step, keep the engine running warm; the eighth step, pull the choke to the full open position; the ninth step, increase and decrease the throttle to normal running. The defects of using the present choke device are that: 1. steps are cumbersome; 2. it is difficult to judge POP sound, the engine is difficult to start; 3. the engine is difficult to start or cannot start at low temperatures (such as 0° C.).
For example, the Publication No. CN1055151C Chinese invention patent, discloses an auxiliary starting passage structure of carburetor, an auxiliary starting body is additionally installed relative to the carburetor body, and on the structural surface is provided with a connecting groove, the connecting groove connects the connecting hole of the main air passage cross hole and the air inlet of auxiliary starting body side to form a subordinate type. But on the bonding surface is not provided with the connecting groove, the bonding surface covers the connecting hole, and in the side of carburetor body sets a cross hole to connect the air inlet and the main hole, the connecting hole of the main hole opening in the mounting seat connect with the air inlet on the bonding surface to form an independent type. The structure of the auxiliary starting passage is complicated, and the operation steps are cumbersome, the engine is difficult to start or cannot start at low temperatures (such as 0° C.).